fix: add missing enchantment effects for rotTouch, soulRend, master, and legendary spells

- Add spell_rotTouch to BASIC_SPELL_EFFECTS (death element Tier 1)
- Add spell_soulRend to TIER2_SPELL_EFFECTS (death element Tier 2)
- Add spell_cosmicStorm, spell_heavenLight, spell_oblivion, spell_deathMark to TIER3_SPELL_EFFECTS (master spells)
- Create legendary-spells.ts with spell_stellarNova, spell_voidCollapse, spell_crystalShatter (legendary spells)
- Update spell-effects/index.ts to include LEGENDARY_SPELL_EFFECTS in SPELL_EFFECTS

Closes #41

docs/project-structure.txt

@@ -204,6 +204,7 @@ Mana-Loop/
 │       │   │   │   ├── spell-effects/
 │       │   │   │   │   ├── basic-spells.ts
 │       │   │   │   │   ├── index.ts
+│       │   │   │   │   ├── legendary-spells.ts
 │       │   │   │   │   ├── lightning-spells.ts
 │       │   │   │   │   ├── metal-spells.ts
 │       │   │   │   │   ├── sand-spells.ts